Charge forming device



Sept. 27, 1 G. c. ROBECHAUD 3,275,307

CHARGE FORMING DEVICE Filed Aug. 2, 1963 2 Sheets-Sheet 1 IN VEN TOR.

WHANN 8 MciWAN/GAL f/arneys fbr A i/mm mmmm United States Patent 3,275,307 CHARGE FGRMING DEVICE Gerald C. Robechaud, Pacific Palisades, Calif, assignor to McCulloch Corporation, Los Angeles, Calif., a corporation of Wisconsin Filed Aug. 2, 1963, Ser. No. 299,530 11 Claims. (Cl. 26136) This invention relates generally to fuel supply systems for internal combustion engines and relates more particularly to a charge forming device for such engines.

While the invention has particular utility embodied in a charge forming device or carburetor for internal cornbustion engines and is shown and described thus embodied, it is to be understood that its utility is not confined thereto.

Certain problems and difficulties are involved in the provisions of charge forming devices or carburetors for internal combustion engines wherein air and fuel for the fuel mixture is drawn into the induction passage of the carburetor by engine suction and mixed therein in the required fuel-to-air ratio. One of such problems is the maintenance of the proper fuel level in the chamber or reservoir supplying fuel to the main fuel nozzle, particularly when the charge forming device is tilted due to tilting of the engine upon which it is installed. As is well known, when such a carbuertor is tilted the fuel-toair ratio is disturbed, causing uneven engine operation, loss of power, or even stopping of the engine. It is therefore an object of the present invention to provide a charge forming device which solves this problem and overcomes the difficulties involved therein.

It is another object of the invention to provide a device of this character wherein the device provides a fuel mixture having substantially constant fuel-to-air ratio under various operating conditions.

It is still another object of the invention to provide a device of this character providing a uniform fuel supply to the induction passage, as required and in accordance with various operating conditions.

It is a further object of the invention to provide a device of this character wherein the level of the fuel supplied to the main fuel nozzle remains substantially constant at various operating attitudes thereof.

It is another object of the invention to provide a charge forming device of this character wherein the level of the fuel supplied to the main fuel nozzle is maintained substantially constant even when the device is tilted.

It is still another object of the invention to provide a device of this character wherein fuel is supplied to the fuel reservoir of the device under super-atmospheric pressure by means of a suitable fuel pump or the like.

A further object of the invention is to provide a device of this character that is reliable in operation.

It is a still further object of the invention to provide a device of this character that has relatively few parts.

It is another object of the invention to provide a device of this character that is relatively inexpensive to manufacture.

The characteristics and advantages of the invention are further sufficiently referred to in connection with the following detailed description of the accompanying drawings, which represent one embodiment. After considering this example, skilled persons will understand that variations may be made without departing from the principles disclosed and I contemplate the employment of any structures, arrangements or modes of operation that are properly within the scope of the appended claims.

Referring to the drawings, which are for illustrative purposes only:

FIG. 1 is a side view of an internal combustion engine Patented Sept. 27, 1 966 ice having a plurality of charge forming devices embodying the present invention operably mounted thereon;

FIG. 2 is a schematic or diagrammatic sectional View of a charge forming device embodying the present invention;

FIG. 3 is a side elevational view of one side thereof;

FIG. 4 is a sectional view taken on line 4-4 of FIG. 2; and

FIG. 5 shows the device as viewed from line 55 of FIG. 2.

Referring more particularly to 'FIG. 1, there is shown an outboard motor or engine, indicated generally at 8, having a plurality of cylinders, not shown, and being of the two-cycle type, although it is to be understood that the engine may be of any other suitable type. Fuel mixture is supplied to the engine by a plurality of charge forming devices or carburetors, indicated generally at 9, and since the carburetors 9 are all of the same construction and operation, a description of one will suflice.

Referring to FIG. 2, there is shown a carburetor body 10 having an induction passage with an air inlet section 11, a fuel mixture outlet section 12 and a venturi 14 provided with a throat 15, said venturi being locate-d between the inlet and outlet sections 11 and 12, respectively. The body 10' has a flange 16 at the free end of the fuel mixture outlet section, said flange having bolt or screw holes 17 therein for bolts or screws 18 whereby the carburetor is operably secured to the engine. A throttle valve 19 of the butterfly type is operably mounted on a throttle shaft 20 in the usual manner by screws 20a, said shaft extending diametrically across the fuel mixture outlet section of the induction passage, being suitably journaled in the walls thereof. Upstream of the throttle shaft there is a stop pin 21 which is press fitted into an opening in the wall of the fuel mixture outlet section, said pin extending a limited distance into the induction passage and being so located as to be in the path of the throttle valve 1-9 when moved in the opening direction so as to limit opening movement of the throttle valve, said opening movement being in clockwise direction, as seen in FIG. 2. The throttle valve 19 is provided with a plurality of openings therethrough adjacent the periphery thereof, as best shown in FIGS. 2 and 5. There are three openings 23a, 23b, and 23c adjacent the lower edge of the throttle valve and annularly spaced apart. Two of these openings, 23a and 23b, are to one side of the vertical diameter of the throttle valve. Opposite these openings is an opening 24 located adjacent the upper edge of the throttle valve and to the opposite side of said vertical diameter.

Carburetor body 10 has oppositely extending lugs 26a and 26b, FIGS. 3 and 5, which have bores that are continuations of the bores through the body 10 and in which the throttle shaft 20 is rotatably mounted. One end of the throttle shaft, FIGS. 3 and 5, extend outwardly of the lug 26a and has a throttle lever 27 secured to the outer end thereof to effect rotative movement of said shaft. Lever 27 is spaced from the outer end of the lug 26a and there is a spring 2-8 operably coiled about that pont-ion of the throttle shaft between lever 27 and said lug 260. One end, 29, of the spring 2 8, is hooked about one edge of the throttle lever and the opposite end 30 of said spring is hooked about the adjacent end of the pin 21 which extends outwardly of the outer end of the adjacent lug 26a. Spring 28 yieldingly urges the throttle shaft in a direction to effect closing of the throttle valve 19.

The body 10 includes a downwardly opening hollow cover 31 which is integral with said body and which has a downwardly opening annular groove 32 in which a gasket 32a is disposed, said groove 32 being adjacent the periphery of the cover. There is also an integral nozzle support means or tube 35 depending from the body in axial alignment with the cover 31, said nozzle support means having a bore 36 extending therethrough. The lower portion 37 of said bore is internally threaded while an upward part 38 of said bore is smooth and unthreaded, and the upper end of said bore 36 terminates within the venturi just ahead of the throat thereof. That is, the upper end of the bore 36 opens into the venturi closely adjacent to but downstream of that portion of the venturi having maximum restriction. Adjacent the lower end the nozzle support is provided with a cross-bore 39 through which fuel is supplied to the bore 36 of the nozzle support. Within the bore 36 the tubular main fuel nozzle 40 has a lower end portion 41 externally threaded for threadable reception in the lower end portion of the bore. The upper end of the fuel nozzle 40 extends into the venturi and the upper or discharge end 42 is normal to the axis of the nozzle and is located at substantially the center of the venturi relative to a plane normal to the axis of the venturi. At its lower end the fuel nozzle is provided with notches 43 for reception of a tool, such as a screwdriver, for screwing the nozzle into the bore 36 and out of said bore or for adjusting the location of the free or discharge end thereof in the venturi. Fuel flowing into the bore 36 of the nozzle support means 35 flows upwardly in the bore 36 int-o the longitudinally extending passage 44 of the main fuel nozzle, said fuel being discharged from the upper end of the nozzle 40 into the stream of air drawn through the induction passage by engine suction to thereby form a combustible fuel mixture for the engine. It is to be understood, of course, that engine suction draws fuel upwardly in the main fuel nozzle and effects discharge of same into the air stream in the induction passage.

Beneath the body of the carburetor is a fuel bowl, indicated generally at 50. It has a bottom wall 51 with an axial bore 52 therein for reception of a screw 53 which is screwed into the lower end of the nozzle support tube 35, the inner end of screw 53 being below the cross-bore or fuel passage 39, as best shown in FIG. 2.

There is a flange 54 extending upwardly from the periphery of the bottom wall 51. The bowl also has a fuel chamber or reservoir 55 defined by a cylindrical wall 56 upstanding from an integral with the bottom wall 51. The wall 56 is coaxial with the flange 54 and also with the nozzle support tube 35, said wall 56 being of greater height than the flange 54, as best shown in FIG. 2. Wall 56 is spaced inwardly of the flange 54 and the channel 57 defined by the flange 54, wall 56 and that that portion of the bottom wall 51 between the flange 54 and 56 serves as a drain channel or trough, fuel being drained from said channel through a drain passage 58 which extends through the flange 54 and a boss 59 extending outwardly of the bowl and being integral there with. A portion of the bore through the nipple 59 is internally threaded for threadable reception of a nipple 60 to which one end of a drain conduit 61 is attached.

Between the flange 54 and the cover 31 is a spacer, indicated generally at 62. Spacer 62 comprises a cylindrical wall 63, a wall 64 extending inwardly from the upper end of the cylindrical Wall 63 and terminating in an upwardly extending flange 65. The lower end of the cylindrical wall 63 of the spacer 62 rests on a shoulder 66 at the upper end of the bowl flange 54 and within an upwardly extending flange 67 of said bowl flange 54 at the outer periphery of shoulder 66 which extends entirely about the upper end of flange 54 inwardly of the retaining flange 67. A gasket 68 is provided in a shallow groove in shoulder 66 at the junction of said shoulder with the inner wall of the positioning flange 67 to thereby provide an effective seal between the lower end of the cylindrical wall 63 and the upper end of the flange 54.

The upstanding flange at the upper end of the spacer is received in the annular groove 32 of the cover 51 and the seal 32a in the upper end of said groove 32 provides an effective sealing means between the upper end of flange 65 and the cover. The length of the nozzle support tube 35 is such that when the screw 53 is tightened the bowl, the spacer 63 and the cover are sealingly secured together.

Fuel reservoir 55 is provided with a cap, indicated generally at 70, which comprises a top wall 71 having at least an interior portion 72 frusto-conical with the smaller end at the top and having an axially arranged overflow opening 74 at the top. Nozzle support tube 35 extends downwardly through the opening 74 which is of greater diameter than that portion of the tube 35 within said opening, thereby providing an annular space about said nozzle support tube 35 and the periphery of the opening 74.

Cap is disposed on the upper free end of the cylindrical wall 56 defining the fuel chamber 55 and has a downturned peripheral flange 75 which extends about an upper peripheral edge portion of said wall 56. The flange 75 has a press fit connection with the upper end portion of the wall 56 to thereby secure the cover in place on said wall 56.

Cap 70 also has an opening 77 through which a fuel inlet conduit 78 extends. This conduit is of resilient material, such as a plastic, and fits snugly in the opening 77 so as to prevent fuel in the chamber or reservoir 55 flowing upwardly or outwardly through said opening 77 past the conduit 78. Fuel conduit 78 is attached to a nipple, indicated at 80 in FIG. 2. This nipple is screwed into a tapped bore provided therefor in the top wall of the cover 31 and said bore connects with a tapped bore in a boss 82, FIG. 1, into which a fixture 83 is screwed and to which one end of a fuel supply conduit 84, FIG. 1, is attached. This conduit is connected with a fuel distributing manifold 85, which in turn is connected, by means of a conduit 86, with a fuel pump 87 of any suitable type. The drain conduit 61 is connected with a fuel return tank 89. The lower end of the fuel return tank is connected with the inlet side of the pump 87 by means of a conduit 90a. There is a main fuel tank 91 which has a fluid connection 92 with a fitting 93 connected with the lower end of the fuel return tank. There is also a fluid connection 94 from the topof the fuel return tank to said fixture 93.

Fuel from the pump 87 is delivered into the fuel reservoir or chamber 25 through the fuel inlet conduit 78. The fuel is continuously pumped into said chamber 55 and when the chamber is full there is an overflow of fuel through the annular space of the opening 74 about the adjacent portion of the main fuel nozzle support means. The overflowing fuel runs into the channel 57 and is drained away therefrom through the drain passage 58 and the fuel return conduit 61, such overflow fuel being carried to the fuel return tank.

Assuming the carburetor is level, the level of the fuel flowing out of the opening 74 will be just above the upper edge of said opening. Fuel in the main nozzle 40 will be at the same level. Tilting of the carburetor, such as may occur under various ordinary operating conditions, will have little effect on the level of the fuel overflowing from the opening 74, particularly at the axial center of said opening and the passage 4-4 of the fuel nozzle 40. Consequently there will be no appreciable change in the quantity or volume of fuel drawn from the main fuel nozzle by engine suction for any particular suction value, so that the ratio of fuel-to-air for the fuel mixture will remain uniform at the desired ratio under various engine operating conditions. I

In order to insure proper drainage of fuel from the drainage channel there is provided an atmospheric Vent therefor 57a having an inlet 57b adjacent the top of the carburetor and an outlet 570 in the cover 31. It is to be noted that the outlet 570 of the atmospheric vent communicates with the upper end of that portion of the bowl assembly communicating with the channel 57. The bowl assembly may be considered the bowl 50 and the spacer 62. It is to be noted that the only tilt for the chamber 55 is that portion of the overflow opening 74 about the main nozzle support tube 35. Fuel is supplied through the fuel chamber 55 at a greater rate than it is drawn into the induction passage of the engine, so that there will be a constant outflow of fuel from the chamber through the overflow opening, the level of fuel flowing from said opening being substantially constant throughout the range of engine operation and under various tilting conditions normally encountered.

A11 idling system is provided which includes an idler tube 99 having its lower end disposed in the fuel reservoir or chamber 55 adjacent the lower end thereof. The idler tube 90 extends upwardly through an opening 91 provided therefor in the cover 31 and venturi wall adjacent the throat of said venturi. The upper end of the tube 90 is received in a bore 92 provided therefor at the diametrically opposite side of the venturi from that part having the bore 91. Tube 90 connects with an idler fuel passage 93 in the body 10, the latter passage being connected with a longitudinally extending passage or bore 94 which has a downturned part 95 terminating in an idling fuel port 96 downstream of the throttle valve 19. Engine suction at the port 96 draws idling fuel from the chamber or reservoir 55 into the fuel mixture section 12. of the induction passage. The openings 23 in the throttle valve 19 provide suffi'cient air for a suitable idling fuel mixture for the engine. In other words, idling fuel is drawn into the fuel mixture section 12 of the carburetor downstream of the throttle valve 19 and is mixed with the air drawn by the engine through the openings 23a, 23b, 23c and 24 in the butterfly disc 19 and this mixture is supplied to the engine for idling purposes.

In connection with the main fuel nozzle, the main fuel nozzle support tube may be considered as part of the main fuel nozzle.

The invention and its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement of the parts of the invention without departing from the spirit and scope thereof or sacrificing its material advantages, the arrangements hereinbefore described being merely by way of example and I do not wish to be restricted to the specific forms shown or uses mentioned except as defined in the accompanying claims, wherein various portions have been separated for clarity of reading and not for emphasis.

I claim:

1. A carburetor comprising:

(A) a carburetor body having a horizontal induction passage therethrough, said induction passage including an air inlet section, a fuel mixture outlet section and a venturi disposed between said sections;

(B) a downwardly facing circular cover at the under side of the carburetor body and integral therewith;

(C) a butterfly throttle valve operably mounted in the mixture outlet section;

(D) a main fuel nozzle support tube integral with the carburetor body and extending downwardly from the cover in axial relationship with said cover, said main nozzle support tube having a tapped bore therethrough and a cross bore adjacent the lower free end;

(B) a tubular fuel nozzle having an externally threaded lower end portion screwed into the tapped bore of the main fuel nozzle support tube, said nozzle being in axial relationship to said support tube, the upper end of said main fuel nozzle extending through an opening provided therefor in the venturi forwardly of the throat thereof, the upper free discharge end of said fuel nozzle being positioned adjacent the axis of said venturi;

(F) a spacer having its upper end sealingly engaging the under side of said cover, said spacer flaring outwardly and having a depending cylindrical wall at the lower end thereof;

(G) a fuel bowl having a bottom wall and a cylindrical wall upstanding from the periphery of said bottom Wall, sealingly engaging the lower end of said spacer; (H) a cylindrical fuel chamber wall integral with the bottom of the fuel bowl and upstanding therefrom to a height greater than the height of the peripheral wall of the bowl and spaced inwardly in axial relationship thereto and to said main nozzle support tube to thereby provide a drainage channel about the lower end of said fuel chamber wall, said drainage channel having a drain outlet communicating therewith adjacent the bottom thereof;

(I) a circular cap secured to the upper end of the fuel chamber wall, said cap having a central portion tapering upwardly and inwardly and having an axially arranged overflow opening through which the main fuel nozzle support tube axially extends, said overflow opening being of greater diameter than that portion of the main nozzle support tube at said opening, said cap having a small notch at one side of the overflow opening and said overflow opening having a fuel inlet tube opening spaced radially outwardly of said overflow opening;

(J) a tubular fixture secured to the carburetor body and depending from the top wall of the cover;

(K) a plastic fuel inlet tube having one end connected to said fixture, said tube depending through the fuel inlet tube opening in sealing engagement with the edge defining said opening;

(L) means for connecting said fixture with a source of fuel for filling the fuel chamber and supplying fuel thereto to effect overflow of fuel from the space of the overflow opening about the :main nozzle support tube .and into the drainage channel; and

(M) an idler fuel supply tube received in the notch at the side of the overflow opening and having its lower end disposed in the fuel supply chamber, said tube extending upwardly diametrically of the throat of the venturi and into the upper side thereof, said carburetor body having an idling fuel discharge port downstream of the upper edge of the throttle valve, there being a fluid passageway connecting said port with the upper end of said idling fuel tube.

2. A carburetor comprising:

(A) a carburetor body having a horizontal induction passage therethrough, said induction passage including an air inlet section, a fuel mixture outlet section and a venturi disposed between said sections;

(B) a downwardly facing circular cover at the under side of the carburetor body;

(C) a butterfly throttle valve operably mounted in the mixture outlet section;

(D) a main fuel nozzle support tube integral with the carburetor body and extending downwardly from the cover in axial relationship with said. cover, said main nozzle support tube having a tapped bore therethrough and a cross bore adjacent the lower free end;

(B) a tubular fuel nozzle having an externally threaded lower end portion screwed into the tapped bore of the main fuel nozzle support tube, said nozzle being in axial relationship to said support tube, the upper end of said main fuel nozzle extending through an opening provided therefor in the venturi forwardly of the throat thereof, the upper free discharge end of said fuel nozzle being positioned adjacent the axis of said venturi;

(F) a spacer having its upper end sealingly engaging the under side of said cover, said spacer flaring outwardly and having a depending cylindrical wall at the lower end thereof;

(G) a fuel bowl having a bottom wall and a cylindrical wall upstanding from the periphery of said bottom wall, sealingly engaging the lower end of said spacer;

(H) a cylindrical fuel chamber wall integral with the bottom of the fuel bowl and upstanding therefrom to a height greater than the height of the peripheral wall of the bowl and spaced inwardly in axial relationship thereto and to said main nozzle support tube to thereby provide a drainage channel about the lower end of said fuel chamber wall, said drainage channel having a drain outlet communicating therewith adjacent the bottom thereof;

(I) a circular cap secured to the upper end of the fuel chamber wall, said cap having a central portion tapering upwardly and inwardly and having an axially arranged overflow opening through which the main fuel nozzle support tube axially extends, said overflow opening being of greater diameter than that portion of the main nozzle support tube at said opening, said cap having a small notch at one side of the overflow opening and said overflow opening having a fuel inlet tube opening spaced radially outwardly of said overflow opening;

(I) a tubular fixture secured to the carburetor body and depending from the top wall of the cover;

(K) a plastic fuel inlet tube having one end connected to said fixture, said tube depending through the fuel inlet tube opening in sealing engagement with the edge defining said opening; and

(L) means for connecting said fixture with a source of fuel for filling the fuel chamber and supplying fuel thereto to eflfect overflow of fuel from the space of the overflow opening about the main nozzle support tube and into the drainage channel.

3. In a charge forming device:

(A) a body having a horizontal induction passage therethrough;

(B) means for supplying fuel to said induction passage, said means including a tubular fuel passage; (C) means defining a fuel chamber having a top wall with an overflow opening therein coaxial with said tubular fuel passage, said tubular fuel passage extending through said overflow opening, the latter having a peripheral portion thereof about said tubular fuel passage for fuel overflow from said chamber;

and

(D) fuel inlet means for said fuel chamber.

4. ha charge forming device:

(A) means defining an induction passage having an air inlet, a fuel mixture outlet and a venturi disposed between said air inlet and fuel mixture outlet;

(B) a main fuel nozzle communicating with said induction passage for discharging fuel into the venturi of said induction passage;

(C) means defining a cylindrical fuel chamber having a top wall, the inner side of said top wall being inclined upwardly and inwardly with an overflow opening coaxial with the axis of said chamber, said main fuel nozzle extending axially through said overflow opening and into said fuel chamber; and

(D) fuel inlet means for said chamber.

5. The invention defined by claim 4, wherein the overflow opening comprises the sole outlet for said fuel chamber.

6. In a charge forming device:

(A) means defining having an inducting passage;

(B) means defining a fuel chamber having a top wall with an overflow opening therein smaller than said chamber and at the highest part of said chamber;

(C) means for supplying fuel to said induction passage, said means including a fuel passage extending into said fuel chamber through said overflow opening, fuel in said fuel chamber being at all sides of said fuel passage; and

(D) means for supplying fuel to said fuel chamber at a greater rate than the fuel withdrawn therefrom.

7. In a charge forming device:

(A) means defining an induction passage;

( 3) '1 Slffilling a fuel chamber having a top wall with an overflow opening therein smaller than said chamber and at the highest part thereof;

(C) means for supplying fuel to said induction passage, said means including a tubular fuel passage extending through said fuel chamber through said overflow opening, fuel in said fuel chamber being at all sides of said fuel passage; and

(D) fuel inlet means for said fuel chamber; and

(E) means for collecting overflow fuel.

8. In a charge forming device:

(A) means defining a horizontal induction passage;

(B) means defining a substantially cylindrical fuel chamber having a top wall with an overflow opening therein;

(C) means for supplying fuel to said induction passage, said means including a tubular fuel passage extending through said overflow opening, said opening being of smaller diameter than the diameter of the fuel chamber;

(D) fuel inlet means for said fuel chamber; and

(E) means defining a trough about said fuel chamber for reception of fuel overflowing from said fuel chamber through said overflow opening.

9. In a charge forming device:

(A) means defining an induction passage having an air inlet, a fuel mixture outlet and a venturi disposed between said air inlet and fuel mixture outlet;

(B) means defining a fuel chamber having a top wall with a central overflow opening;

(C) a main fuel discharge means discharging into said induction passage, said fuel discharge means including a tubular fuel passage extending centrally through said overflow opening; and

(D) fuel inlet means for said fuel chamber,

(B) said top wall being inclined upwardly and toward said central overflow opening.

10. In a charge forming device:

(A) means defining an induction passage having an air inlet, a fuel mixture outlet and a venturi disposed between said air inlet and fuel mixture outlet;

(B) means defining a fuel chamber having a top wall with a central overflow opening;

(C) a main fuel discharge means discharging into said induction passage, said fuel discharge means including a tubular fuel passage extending centrally through said overflow opening;

(D) fuel inlet means for said fuel chamber,

(E) said top wall being inclined upwardly and toward said central overflow opening,

(F) said top wall having a second opening therein,

(G) said fuel inlet means including a fuel conduit extending through said second opening; and

(H) means providing a seal between said conduit and the edge defining said second opening.

11. In a charge forming device:

(A) means defining an induction passage;

(B) means defining a fuel chamber having a top wall with an overflow opening therein;

(C) means for supplying fuel to said induction passage, said means including a tubular fuel passage extending through said overflow opening; and

(D) fuel inlet means for said fuel chamber,

(B) said overflow opening being smaller than the cross-sectional area of the fuel chamber.

References Cited by the Examiner UNITED STATES PATENTS HARRY B. THORNTON, Primary Examiner.

T. R. MILES, Assistant Examiner. 

3. IN A CHARGE FORMING DEVICE: (A) A BODY HAVING A HORIZONTAL INDUCTION PASSAGE THERETHROUGH; (B) MEANS FOR SUPPORTING FUEL TO SAID INDUCTION PASSAGE, SAID MEANS INCLUDING A TUBULAR FUEL PASSAGE; (C) MEANS DEFINING A FUEL CHAMBER HAVING A TOP WALL WITH AN OVERFLOW OPENING THEREIN COAXIAL WITH SAID TUBULAR FUEL PASSAGE, SAID TUBULAR FUEL PASSAGE EXTENDING THROUGH SAID OVERFLOW OPENING, THE LATTER 